This is the National Destination Code(NDC):306 page list. Its detail is as below.
Area code 306 is one of the original 86 area codes created by AT&T and the Bell System in 1947. It originally served the entire province of Saskatchewan. In 2013, area code 639 was created as an overlay to area code 306. Currently, it covers the entire state of Saskatchewan, and it overlaps coverage areas with area code 639.